In my opinion, LET THE PRICES DROP. You know what I believe will happen? New waves of investors will "get in" while they can as prices plummit which will certainly help to stimulate prices. Also, we all know how BIG of a player the PRESS is when it comes to spreading the word about cryptos. In fact, poor press coverage is responible for many ICO failures.
My reason for mentioning the media up is that no news is bad news; no coverage is bad coverage. As we see such large percentile drops within a short period of time (this is the lowest of the year) more outlets will begin to release publications covering the topic.
This means, quite literally, that the declining prices can (and probably will) not only have a turning point but a strong one at that.
For people who believe that someday bitcoin prices will soar compared to today's prices, of course the current price, when there is a decline, is a good opportunity for them to start investing their money. But for those who are hesitant or even do not believe in the future of bitcoin, they are free to sell the assets they have. So, what to do is depends on the confidence of each individual.